I will look at Jill's link (tnx!) and hope to find an indication of "how many" I should use. My main concern is that I do not want to use too many as to be black listed because considered spam, but then again, I don't know what too many is...
I was just passing and I noticed your post. Now, I get asked these very same questions a lot.
I want you to think about a few things here. If you had written a book about 20th century verse called “Poems of the 20th Century”: How many characters would be required to write down the title of your book?
If you went to the library and looked at one of the record cards for a book on 20th century verse and saw the keywords: poems, poetry, verse, rhymes: How many more words would be necessary before you got the “gist” of what the book is about?
If someone wrote a piece about your book and described it as “ a book about popular poems of the 20th century”: Would you agree that sums up exactly what it is?
So the answer is not so difficult: why would you use MORE or LESS words than those which are required to make it fully understood, to both man and machine i.e. search engine, what your web pages are about?
Think about each of your web pages as being like the book. And give each page its “due” identity, so there’s no confusion in the meta data or the text on the page of what the subject matter is.
How many characters a search engine would accept in any given tag is not an indication of how many you’re actually *required* to use.
Here’s something which is more important to remember. Make it clear exactly what your page is about i.e. by having a sensible title tag which relates to the actual content on the page. And if other pages which point to you use those words in the anchor text of the link: then you have the *start* of a beautiful search engine relationship.